Impeller for axial-flow heat-dissipating fan

ABSTRACT

An impeller for an axial-flow heat-dissipating fan includes a hub and a plurality of blades symmetrically formed on an outer periphery of the hub and extending in an inclined angle with respect to a longitudinal direction parallel to a rotational axis of the hub. Each blade includes a leading edge, a trailing edge, a radial inner edge, and a radial outer edge. Two adjacent blades overlap with each other in the longitudinal direction such that each blade has first and second overlapped areas. The first overlapped area on each blade extends outward from the leading edge and the radial inner edge but spaced from the radial outer edge of the blade. The second overlapped area on each blade extend outward from the trailing edge and the radial inner edge but spaced from the radial outer edge of the blade. The air inlet amount is increased and blowing noise is lowered.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an impeller. In particular, the present invention relates to an impeller for an axial-flow heat-dissipating fan.

2. Description of Related Art

FIG. 1 of the drawings illustrates an impeller 10 for an axial-flow heat-dissipating fan. The impeller 10 is mounted in a casing 20 and includes a hub 101 and a plurality of blades 102. Each blade 102 is mounted on an outer periphery of the hub 101 in an inclined angle. The blades 102 drive air to flow in an axial direction. Due to limitation of release of the mold forming the impeller 10, two blades 102 adjacent to each other cannot overlap with each other when viewed from the longitudinal direction parallel to the rotational axis of the impeller 10. The total amount of air driven by the impeller 10 is in proportion to the number or total air-driving area of the blades 102. In other words, the total amount of air driven by the impeller 10 can be increased only by overcoming the release limitation of the mold.

A complex impeller consisting of two hub parts have been disclosed in, e.g., U.S. Pat. Nos. 6,318,964 and 6,572,336. As illustrated in FIGS. 2 and 3, such a complex impeller 3 comprises a shaft 30, a complex hub 31, and a plurality of blades 32. The complex hub 31 includes an upper hub 31 a and a lower hub 31 b. A plurality of upper blades 32 a are formed on an outer periphery of the upper hub 31 a, and a plurality of lower blades 32 b are formed on an outer periphery of the lower hub 31 b, with the upper blades 32 a and the lower blades 32 b together forming the blades 32. Each blade 32 overlaps with an adjacent blade 32 when viewed from a longitudinal direction parallel to the shaft 30.

As illustrated in FIG. 3, after assembly, the leading edge 321 of each blade 32 is coincident with the trailing edge 322 of an adjacent blade 32. By such an arrangement, the number of the blades 32 and the total air-driving area of the blades 32 are increased. However, the blades 3 are not disposed properly such that the blowing noise is high.

OBJECTS OF THE INVENTION

An object of the present invention is to provide an impeller for an axial-flow heat-dissipating fan for increasing the air inlet amount driven by the impeller.

Another object of the present invention is to provide an impeller for an axial-flow heat-dissipating fan with lowered blowing noise. SUMMARY OF THE INVENTION

An impeller for an axial-flow heat-dissipating fan in accordance with the present invention comprises a hub including an outer periphery and a plurality of blades symmetrically formed on the outer periphery of the hub and extending in an inclined angle with respect to a longitudinal direction parallel to a rotational axis of the hub. Each blade includes a leading edge, a trailing edge, a radial inner edge, and a radial outer edge. Two of the blades adjacent to each other overlap with each other in the longitudinal direction such that each blade has a first overlapped area and a second overlapped area.

The first overlapped area on each blade extends outward from the leading edge and the radial inner edge but spaced from the radial outer edge of the blade. The second overlapped area on each blade extend outward from the trailing edge and the radial inner edge but spaced from the radial outer edge of the blade. The air inlet amount is increased and blowing noise is lowered.

The trailing edge of each blade projects on an adjacent blade along a rear projection line. The first longitudinal overlapped area is defined by the rear projection line, the leading edge of the adjacent blade, and the radial inner edge of the adjacent blade.

The leading edge of each blade intersects the radial inner edge of the blade at a front base point. The rear projection line intersects the leading edge of the adjacent blade at a first overlapped point. A distance between the front base point and the overlapped point is ⅕-⅘ of a length of the leading edge.

The rear projection line intersects the radial inner edge of the adjacent blade at a second overlapped point. A distance between the front base point and the overlapped point is ⅙-⅚ of a length of the radial inner edge.

The trailing edge of each blade projects on an adjacent blade along a front projection line. The second longitudinal overlapped area is defined by the front projection line, the leading edge of the adjacent blade, and the radial inner edge of the adjacent blade. The trailing edge of each blade intersects the radial inner edge of the blade at a rear base point. The front projection line intersects the trailing edge of the adjacent blade at a third overlapped point. A distance between the rear base point and the overlapped point is ⅕-⅘ of a length of the trailing edge. The front projection line intersects the trailing edge of the adjacent blade at a fourth overlapped point. A distance between the rear base point and the overlapped point is ⅙-⅚ of a length of the trailing edge.

Preferably, the leading edge of each blade is at an angle between 10 degrees and 90 degrees with the trailing edge of an adjacent blade when viewed from the longitudinal direction parallel to the rotational axis of the hub.

The leading edge of each blade intersects the radial outer edge of the blade at a front end point. The trailing edge of each blade intersects the radial outer edge of the blade at a rear end point. Preferably, a line passing through the front end point of the leading edge and the rear end point of the trailing edge of each blade is at an angle between 10 degrees and 70 degrees with a plane orthogonal to the rotational axis of the hub.

Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a conventional impeller for an axial-flow heat-dissipating fan;

FIG. 2 is a side view of another conventional impeller for an axial-flow heat-dissipating fan;

FIG. 3 is a top view of the impeller in FIG. 2;

FIG. 4 is an exploded perspective view of an axial-flow heat-dissipating fan with an impeller in accordance with the present invention;

FIG. 5 is an enlarged view of a circled portion in FIG. 4;

FIG. 6 is a top view of the impeller in accordance with the present invention;

FIG. 7 is a side view of the impeller in accordance with the present invention; and

FIG. 8 is a perspective view of the impeller in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 4 shows an axial-flow heat-dissipating fan with an impeller 4 in accordance with the present invention. The axial-flow heat-dissipating fan includes a casing 5 for accommodating the impeller 4. A motor 6 is mounted in the casing 5 for driving the impeller 4 to turn.

Referring to FIGS. 4 and 5, the impeller 4 comprises a shaft 40 (see FIG. 7), a hub 41, and a plurality of blades 42. The shaft 40 extends from a center of an inner face of the hub 41 for coupling with the motor 6.

The blades 42 are symmetrically formed on an outer periphery of the hub 41 and extend in an inclined angle with respect to a longitudinal direction parallel to an extending direction of the shaft 40 (i.e., the rotational axis of the hub 41). Each blade 42 includes a leading edge 421 on an air inlet side of the blade 42, a trailing edge 422 on an air outlet side of the blade 42, a radial inner edge 423 on the outer periphery of the hub 41, and a radial outer edge 424 distal to the outer periphery of the hub 41. The leading edge 421, the trailing edge 422, the radial inner edge 423, and the radial outer edge 24 are rectilinear or curved with an appropriate radius of curvature according to product needs. For each blade 42, the leading edge 421 intersects the radial inner edge 423 at a front base point 11, the leading edge 421 intersects the radial outer edge 424 at a front end point 12, the trailing edge 424 intersects the radial inner edge 423 at a rear base point O1, and the trailing edge 424 intersects the radial outer edge 424 at a rear end point O2, best shown in FIG. 5.

Still referring to FIGS. 4 and 5, in a longitudinal direction parallel to the extending direction of the shaft 40, the trailing edge 422 of each blade 42 projects on an adjacent blade 42 along a rear projection line L1 that intersects the leading edge 421 of the adjacent blade 42 at a first overlapped point P1 and that intersects the radial inner edge 423 of the adjacent blade 42 at a second overlapped point P2. A first longitudinal overlapped area A1 is defined by the rear projection line L1, the leading edge 421 of the adjacent blade 42, and the radial inner edge 423 of the adjacent blade 42.

The distance between the front base point I1 and the first overlapped point P1 is preferably ⅕-⅘ (most preferably ½) of a length of the leading edge 421. Further, the distance between the front base point 11 and the second overlapped point P2 is preferably ⅙-⅚ (most preferably ½) of a length of the radial inner edge 423.

Still referring to FIGS. 4 and 5, in the longitudinal direction parallel to the extending direction of the shaft 40, the leading edge 421 of each blade 42 projects on the other adjacent blade 42 along a front projection line L2 that intersects the trailing edge 422 of the other adjacent blade 42 at a third overlapped point P3 and that intersects the radial inner edge 423 of the other adjacent blade 42 at a fourth overlapped point P4. A second longitudinal overlapped area A2 is defined by the front projection line L2, the trailing edge 422 of the other adjacent blade 42, and the radial inner edge 423 of the other adjacent blade 42.

The distance between the rear base point O1 and the third overlapped point P3 is preferably ⅕-⅘ (most preferably ½) of a length of the trailing edge 422. Further, the distance between the rear base point O1 and the fourth overlapped point P4 is preferably ⅙-⅚ (most preferably ½) of a length of the radial inner edge 423.

Referring to FIG. 6, when viewed from the longitudinal direction parallel to the extending direction of the shaft 40, the leading edge 421 of each blade 42 is at an angle θ1 with the trailing edge 422 of an adjacent blade 42.

The angle θ1 is preferably between 10 degrees and 90 degrees, and most preferably 45 degrees. Further, the rear projection line L1 on each blade 42 is at the same angle θ1 with the front projection line L2 on an adjacent blade 42. Further, the first overlapped area A1 and the second overlapped area A2 are spaced from the radial outer edge 422 of each blade 42.

Referring to FIG. 7, a line L passing through the front end point 12 of the leading edge 421 on each blade 42 and the rear end point O2 of the trailing edge 422 of the blade 42 is at an angle θ2 with a plane P orthogonal to the extending direction of the shaft 40. The angle θ2 is preferably between 10 degrees and 70 degrees, and most preferably 30 degrees.

Referring to FIG. 4, the casing 5 includes an airflow passage 50, an air inlet 51, an air outlet 52, a base 53, and a plurality of ribs 54. The base 53 is located in the air outlet 52 side and supported by the ribs 54 that are connected to an inner periphery delimiting the airflow passage 50. The motor 6 is mounted on the base 54 for coupling with and driving the impeller 4. The ribs 54 may extend in an appropriate inclination angle in the air-driving direction to provide a guiding function as well as a pressure-boosting effect.

Referring to FIGS. 5 and 8, the impeller 4 is mounted on the casing 5 to form an axial-flow heat-dissipating fan. In operation, the impeller 4 drives air into the airflow passage 50 via the air inlet 51. The airflow is boosted by the ribs 54 and then exits the casing 5 via the air outlet 52. For each blade 42 and two blades 42 adjacent to the blade 42, each blade 42 has a first overlapped area A1 with one of the two adjacent blades 42 and a second overlapped area A2 with the other adjacent blade 42. None of the first overlapped area A1 and the second overlapped area A2 extend to the radial outer edge 422 of the blade 42. By such an arrangement, the number of the blades 42 and the total air-driving area of the blades 42 of the impeller 4 in accordance with the present invention are increased as compared to the conventional impeller 1 in FIG. 1. Further, overlapping of the blades 42 in the area adjacent to the radial outer edge 424 is avoided in the impeller 4 in accordance with the present invention as compared to the conventional impeller 3 in FIGS. 2 and 3. The blowing noise is lowered and the air amount driven by the impeller 4 is increased.

While the principles of this invention have been disclosed in connection with a specific embodiment, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims. 

1. An impeller for an axial-flow heat-dissipating fan, comprising: a hub including an outer periphery; and a plurality of blades symmetrically formed on the outer periphery of the hub and extending in an inclined angle with respect to a longitudinal direction parallel to a rotational axis of the hub; each said blade including a leading edge, a trailing edge, a radial inner edge, and a radial outer edge; two of the blades adjacent to each other overlapping with each other in the longitudinal direction such that each said blade having a first overlapped area and a second overlapped area; the first overlapped area on each said blade extending outward from the leading edge and the radial inner edge but spaced from the radial outer edge of the blade, the second overlapped area on each said blade extending outward from the trailing edge and the radial inner edge but spaced from the radial outer edge of the blade, thereby increasing an air inlet amount and lowering blowing noise.
 2. The impeller for an axial-flow heat-dissipating fan as claimed in claim 1 wherein the trailing edge of each said blade projects on an adjacent blade along a rear projection line, and wherein the first longitudinal overlapped area is defined by the rear projection line, the leading edge of the adjacent blade, and the radial inner edge of the adjacent blade.
 3. The impeller for an axial-flow heat-dissipating fan as claimed in claim 2 wherein: the leading edge of each said blade intersects the radial inner edge of the blade at a front base point; the rear projection line intersects the leading edge of the adjacent blade at an overlapped point; and a distance between the front base point and the overlapped point is ⅕-⅘ of a length of the leading edge.
 4. The impeller for an axial-flow heat-dissipating fan as claimed in claim 2 wherein: the leading edge of each said blade intersects the radial inner edge of the blade at a front base point; the rear projection line intersects the radial inner edge of the adjacent blade at an overlapped point; and a distance between the front base point and the overlapped point is ⅙-⅚ of a length of the radial inner edge.
 5. The impeller for an axial-flow heat-dissipating fan as claimed in claim 1 wherein the trailing edge of each said blade projects on an adjacent blade along a front projection line, and wherein the second longitudinal overlapped area is defined by the front projection line, the trailing edge of the adjacent blade, and the radial inner edge of the adjacent blade.
 6. The impeller for an axial-flow heat-dissipating fan as claimed in claim 5 wherein: the trailing edge of each said blade intersects the radial inner edge of the blade at a rear base point; the front projection line intersects the trailing edge of the adjacent blade at an overlapped point; and a distance between the rear base point and the overlapped point is ⅕-⅘ of a length of the trailing edge.
 7. The impeller for an axial-flow heat-dissipating fan as claimed in claim 5 wherein: the trailing edge of each said blade intersects the radial inner edge of the blade at a rear base point; the front projection line intersects the radial inner edge of the adjacent blade at an overlapped point; and a distance between the rear base point and the overlapped point is ⅙-⅚ of a length of the radial inner edge.
 8. The impeller for an axial-flow heat-dissipating fan as claimed in claim 1 wherein: the leading edge of each said blade is at an angle between 10 degrees and 90 degrees with the trailing edge of an adjacent blade when viewed from the longitudinal direction parallel to the rotational axis of the hub.
 9. The impeller for an axial-flow heat-dissipating fan as claimed in claim 1 wherein: the leading edge of each said blade intersects the radial outer edge of the blade at a front end point; the trailing edge of each said blade intersects the radial outer edge of the blade at a rear end point; a line passing through the front end point of the leading edge and the rear end point of the trailing edge of each said blade is at an angle between 10 degrees and 70 degrees with a plane orthogonal to the rotational axis of the hub.
 10. The impeller for an axial-flow heat-dissipating fan as claimed in claim 3 wherein: the rear projection line intersects the radial inner edge of the adjacent blade at a second overlapped point; and a distance between the front base point and the second overlapped point is ⅙-⅚ of a length of the radial inner edge.
 11. The impeller for an axial-flow heat-dissipating fan as claimed in claim 10 wherein the trailing edge of each said blade projects on an adjacent blade along a front projection line, and wherein the second longitudinal overlapped area is defined by the front projection line, the trailing edge of the adjacent blade, and the radial inner edge of the adjacent blade.
 12. The impeller for an axial-flow heat-dissipating fan as claimed in claim 11 wherein: the trailing edge of each said blade intersects the radial inner edge of the blade at a rear base point; the front projection line intersects the trailing edge of the adjacent blade at a third overlapped point; and a distance between the rear base point and the third overlapped point is ⅕-⅘ of a length of the trailing edge.
 13. The impeller for an axial-flow heat-dissipating fan as claimed in claim 12 wherein: the front projection line intersects the trailing edge of the adjacent blade at a fourth overlapped point; and a distance between the rear base point and the fourth overlapped point is ⅙-⅚ of a length of the trailing edge. 